Hello, I was browsing a derivation for the relationship between the curvature of horizontal road curves and the angle of elevation/banking. The derivation is shown on page 4 here: http://www.cdeep.iitb.ac.in/nptel/Civil%20Engineering/Transportation%20Engg%201/14-Ltexhtml/nptel_ceTEI_L14.pdf [Broken] There is one thing I cannot understand. Everything revolves around centrifugal force. It is here treated as a force having the same magnitude of a centripetal force but in the opposite direction. Basically the derivation is done by first finding the component of the weight in the direction of the slope. The centrifugal force is then resolved and then force balance is used to equate the forces. (all in the direction parallel to the slope) So my questions are: 1. If we resolve the component of weights and friction in the horizontal direction (instead of resolving the centrifugal force), we do not reach the same equation. 2. Where does centrifugal force come into action? This force does not exist from my knowledge of circular motion. Only centripetal force exists. This returns us to 1. , why not resolve the weight and frictional forces in the horizontal direction and equate the forces. Thank you.